Stepped trim tab

ABSTRACT

The invention relates to a trim tab for watercraft, the inclinable tab of which has gradations having breaking edges, and in front of the sections having a breaking edge on the bracket. The active cylinder is assisted by a gas spring which may also be blockable, and which is released by means of the active cylinder. Underwater lamps that are affixed on the outflow side have a spread angle, and the underwater lamps have a metal housing which is connected to the tab for dissipating waste heat.

TECHNICAL FIELD

The invention is directed to a trim tab, having a graduated base and side walls, for watercraft, according to the preamble of Claim 1.

PRIOR ART

Trim tabs are used for improving the glide angle of watercraft, and displace the corresponding buoyancy zones by means of flow deflections to allow more favorable weight distributions and/or to facilitate quicker initiation of gliding of the vehicle, as described in U.S. Pat. No. 3,628,487 or also US 2004/0014376 A1.

Recently, other systems on the market, for example lowerable damming wedges, have been described in patents TW 499382 B and U.S. Pat. No. 6,006,689, among others.

It is now becoming increasingly common to mount underwater lamps on trim tabs, since trim tabs do not require large mounting holes in the side of the ship.

DESCRIPTION OF THE INVENTION

For a trim tab for watercraft of the type mentioned at the outset, the object of the invention is to achieve effective trim with maximum buoyancy and minimum resistance values at lower as well as higher speeds, which is accomplished by graduating the base surface of the trim tab and at the same time raising the side walls at the trim tab. The action of the active cylinder for displacing the trim tab is assisted by means of a gas traction spring or gas pressure spring. In addition, the trim tab should generate a specialized light at night which allows consistent safety-relevant visibility when maneuvering in a port where there is minor light pollution, and which at the same time creates a specialized lighting effect at the stern of a watercraft, which may be directed onto the specialized trim tab and which allows effective heat dissipation by means of suitable materials.

Trim tabs are indispensible in watercraft, and as the result of lowering one or both tabs, a change in the vehicle position in the water is produced which in the longitudinal axis should be as horizontal as possible, and in the transverse axis should have a slightly positive setting angle, so that the vehicle is able to glide through the water with the least resistance possible, and the passengers thus automatically have a better feeling of well-being when the base of the vehicle is more or less horizontal and steady in the water. This is made possible by means of one or more gradations having breaking edges on the trim tab base, which allows use of longer trim tabs, and thus, production of the same change in trim angle on the vehicle as with short trim tabs, at a smaller setting angle, and at the same time with lower overall resistance. At higher speeds, at which the resistance is disproportionately noticeable, the wetted surface area is decreased by means of the gradations, so that above a certain speed the friction has little or no action due to the fact that the flow breaks away at the gradations of the trim tab, and therefore the contact surface of the trim tab base with the water is separated, the frictional resistance is thus reduced, and a higher final speed of the vehicle is made possible or less fuel consumption results. The gradations may also be easily produced by cutting plastic plates to various lengths and sharply contouring them on the outflow side and connecting them to the tab, which at the same time results in a desired reinforcement of the trim tab and thus subjects the tab to less torsion.

It is self-evident that, by means of the longer trim tabs on the exterior of a watercraft, rolling while at anchor as well as pitching due to the lever length of the trim tabs is improved, since the trim tabs act as baffle plates or stabilizers.

The primary purpose of raising the side walls at the trim tabs is to ensure that little or no water flows onto the tabs at moderate speeds, so as to consistently guarantee optimal buoyancy, and at the same time to positively influence the flow and produce a type of artificial extension of the hull; otherwise, the flow would combine at the stern too quickly, possibly resulting in corresponding turbulence, even eddying, which is extremely detrimental for the efficiency of a hull.

The active cylinder may also be assisted by a gas spring. In particular for an electric active cylinder having a spindle; this results in a new concept of activation, since the gas spring may provide practically the same extension force as the active cylinder, and therefore the overall power for lowering the trim tab may be almost doubled. For this purpose, the active cylinder must correspondingly deliver more power during raising of the trim tab, since the gas spring always presses against same. In addition, the gas spring may be blocked by means of a check valve, so that the entire load of the trim tab does not rest on the spindle and spindle nut, but instead, the load is also supported by the gas spring.

Furthermore, underwater lamps are mounted on the trim tab with a deflection angle from one underwater lamp to the other, so that good illumination of the body of water downstream from the watercraft is still achieved, using focused light with fewer powerful lamps for this purpose, and thus eliminating the light pollution, which now also surrounds the vicinity of the body of water, without impairing the quality of the visibility conditions.

According to the invention, this is achieved by the features of claim 1, which by means of gradations on the tab base allow the flow to break away cleanly in each case at appropriate speeds by means of breaking edges, and thus allow the resistance to be reduced, resulting in a higher final speed of the vehicle or less fuel consumption at cruising speed, and by means of a gas spring are used as assistance for the active cylinder and the appropriately placed underwater lamps, which require less power and less light and nevertheless allow equivalent safety-relevant visibility downstream from the watercraft compared to conventional, more powerful lamps. The core of the invention is to achieve a completely efficient trim tab which uses less energy and achieves the same or better results with regard to trim of a watercraft by means of gradations and breaking edges, to assist the active cylinder in terms of force by means of a gas spring, and to ensure good visibility at night downstream from a watercraft, using less light energy.

Further advantageous embodiments of the invention result from the subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained in greater detail below with reference to the drawings. Identical elements are provided with the same reference numerals in the various figures.

The drawings show the following

FIG. 1 shows a schematic side view of a graduated trim tab which is pivotably mounted to the stern of a watercraft by means of a bracket, together with an active cylinder and a gas spring, as well as a blocking cable for the gas spring; and

FIG. 2 shows a schematic three-dimensional view of a graduated trim tab having the gradations, the fastening for the active cylinder by means of an emergency bolt, and the reinforcements on the base plate, the side walls, and the individually angled underwater lamps.

Only the elements which are essential for the direct understanding of the invention are schematically shown.

APPROACH TO CARRYING OUT THE INVENTION

FIG. 1 shows a schematic side view of a trim tab 1, having gradations 2 on the tab 3, at the stern 4 of a watercraft, and an active cylinder 5 and a gas spring 6, both of which are mounted and supported on the one hand at the stern 4 and on the other hand at the trim tab 1, by means of bearing elements 7.

The trim tab 1, one of which is mounted on each side at the stern 4 of a watercraft, may be adjusted in inclination via the pivot DP by means of an active cylinder 5 in order to influence the trim position of a watercraft. During acceleration of the vehicle, for example, both trim tabs 1 are simultaneously pivoted downwardly according to the arrow H, so that during the acceleration phase the stern 4 is lowered to a lesser extent, i.e., the bow of the vehicle is thus raised to a lesser extent, and therefore the acceleration of the vehicle as well as the visibility toward the front are improved. In contrast, the individual control of the trim tab 1 is used to balance the vehicle in the most horizontal position possible; otherwise, the vehicle would have an oblique position due to a crosswind or nonuniformly distributed weight.

The active cylinder 5 may be a hydraulic or electric active cylinder having a spindle drive, and may be assisted by a gas spring 6. Steel springs on an active cylinder 5 for the trim tab 1 are known, and are used to raise the tabs 3 back, thus sparing a hydraulic valve and a fluid line. The drawback is the unfavorable spring rate, which is ideally released by means of a gas traction spring 6 a mounted on the trim tab 1, since gas springs have the special property of having a flat spring rate. The total forces on the hydraulic active cylinder 5 are thus reduced, on the one hand in order to move the tab 3 downwardly during flow S of the water, and on the other hand to overcome the force of the steel or plastic spring rate, which also has an increasingly unfavorable effect during the pivoting H. For electric spindle drives having a self-locking spindle, the gas spring 6 in such a case is used as a power booster, in that the gas spring 6 acts as a gas pressure spring 6 b. In this way, an electric spindle drive together with the gas pressure spring 6 b may provide almost twice the force. During retraction, i.e., during raising of the tab 3, the electric spindle drive must overcome the force of the gas pressure spring 6 b minus the pressure of the flow S of water onto the tab 3 and gradations 2 during travel of the watercraft.

The use of longer trim tabs 1 is often attributed to the insufficient action of the active cylinder 5, in particular the electric active cylinder; the trim tabs may now be released in a cost-effective and rapid manner by means of such gas springs 6.

It is also conceivable to use a blockable gas spring 6 c which has a check valve 17 inside the gas spring 6 c, and a release cable 18 which is connected to an electric release head 19. When the active cylinder 5 is activated, the release head 19 is also activated at the same time or with a time delay, so that the blocking at the gas spring 6 c is eliminated. When the active cylinder 5 is stopped, the release head 19 is also stopped, i.e., released. Higher retention forces are thus achievable, and active cylinders 5 with a nonself-locking spindle may also be used. In addition, washing of waves is not completely transmitted to the spindle and spindle nut.

Trim tabs 1 have the advantage of transferring a watercraft into a favorable trim position, and on the other hand they have the disadvantage that the wetted surface area of the tabs 3 results in friction due to the flow, which is detrimental to power. Studies have shown that the widely held view that the problem is solved by raising the tab 3 is incorrect, since in this case the Coanda effect acts, and therefore the flow does not break away; rather, the flow S makes contact even when the tab 3 is raised, thus generating friction and having an adverse impact on the power. This effect is further intensified by a longer trim tab 1, and the advantage of the longer trim tab 1, with a smaller pivot H of the setting angle of the tab 3 in order to be able to correctly trim the watercraft, and with a smaller flow resistance, is negated, since at the same time, at higher travel speeds of the watercraft the friction of the flow has a noticeable negative impact due to the fact that for a given speed, a higher rotational speed is required and therefore the fuel consumption increases.

The Coanda effect is overcome by means of gradations 2 on the tab 3, in that the individual gradations 2 have a breaking edge 8, so that the flow S breaks away cleanly at this location, and there is no longer flow against the gradation 2 thereabove, except for water spray, which does not have measurable effects on the power of the watercraft.

The watercraft now has the considerable advantage that at low speeds the hull is extended due to the trim tab 1, and higher stability of the vehicle is provided; the higher the speed when the watercraft is underway, the shorter the overall stern length becomes, by means of which release of the flow S at the particular breaking edge 8 at the gradations 2, and thus the detrimental friction of the flow S, becomes ineffective. The individual phases are indicated as follows: beginning at the resting position or displacement travel of the watercraft, the waterline is WL 1; for low-speed gliding of the watercraft the waterline is WL 2; and at high speed of the watercraft the waterline is WL 3. It is ideal when there is a breaking edge 8 a even at the stern 4 of the watercraft, which anticipates a positive effect on the trim tab 1 at this location. The trim tab may advantageously be integrated directly onto the bracket 20, which is affixed to the stern 4 by means of the edge strip 21, and thus also simplifies the mounting placement of the trim tab 1; at the same time, the tab 3 is raised and thus acts as a gradation 2. The breaking edge 8, 8 a is characterized by being sharp-edged, i.e., having no roundings, so that the water is given no opportunity to follow a corresponding rounding. Due to the side walls 9, at moderate speeds of the watercraft the trim tab 1 acquires effective buoyancy more rapidly, and preferably little, or ideally no, water flows onto the tab 3, which in turn generates friction and represents weight. The side walls 9 also have the effect of artificially extending the hull, in that the flow only then further combines downstream from the stern 4, thus eliminating the risk of detrimental turbulence or eddy effects on the stern 4. The side walls 9 should be at least 50 mm high in order to achieve a measurable result, and preferably should be mounted at an angle of 90° or greater with respect to the tab 3. It is advantageous for the side walls 8 to be raised on both sides of the tab, so that preferably little or no water collects on the tab 3. A mechanical connection of the side walls 9 to the lamp support 14 shown in FIG. 2 has the advantage that the lamp support 14, i.e., the underwater lamps 16, is/are not able to vibrate during travel, which is advantageous for the service life of the light source and is useful for reinforcement of the overall trim tab 1. Not shown are slits or the like at the side of or on the outflow side of the trim tab 1, which allow water present on the trim tab 1 to flow off as quickly as possible.

FIG. 2 shows a schematic three-dimensional view of a trim tab 1 having the gradations 2 on the tab 3, and a fastening 10 for the active cylinder 5 by means of an emergency bolt 11 which is passed through the opening 12 in the side wall 9, and the reinforcements 13 on the tab 2, which also has a lamp support 14 in which lamp sockets 15 are mounted and which accommodate the underwater lamps 16.

If the active cylinder 5, in particular an electric active cylinder having a self-locking spindle, should fail, it is difficult to bring the tab 3 back into the raised position in the event that the active cylinder 5 does not have an emergency crank, which would also have to be appropriately accessible. The solution is an emergency bolt 11, which is used primarily as a bearing element 7 and also for decoupling the active cylinder 5 from the tab 3, the emergency bolt being passed through the opening 12 in one of the two side walls 7 and advantageously having a clip or an angled end in order to pull the emergency bolt 11 manually, and thus separate the active cylinder 5 from the fastening 10. At the same time, the emergency bolt 11 is prevented from axial detachment by retaining means (not shown here), for example a lock washer, snap ring, or supported spring. The emergency bolt 11 may also have a shorter design and not be guided through the opening 12, in the case that an observation cover is not mounted on the trim tab 1. The emergency bolt 11 may also be mounted on the upper bearing element 7, which supports the active cylinder 5 on the stern 4.

Unfortunately, the demand for underwater lamps 16 having increasingly more intense illumination contributes to general light pollution. Instead of mounting increasingly more intense lighting behind the stern 4, by means of the present invention the underwater lamp 16 is mounted at a defined separate angle with respect to the next underwater lamp 16, with a specified light cone, usually having a value between 12° and 35°. If three underwater lamps 16 are mounted, they are situated with respect to one another at a lamp spread angle a to b to c, and thus likewise result in a broadly fanned-out light, but with three bundled light beams. Sufficient illumination is thus ensured at the stern 4 in order to provide good underwater vision during port maneuvering; the spread light cones also result in an independent light image, in that every two underwater lamps 16 form a V-shaped light beam with respect to one another in the water; i.e., in addition to the known basic parameters of an underwater lamp 16, such as lumens and beam angles, in the present case the spread angle a to b to c of one underwater lamp 16 to another is indicated. Furthermore, the individual underwater lamps 16 may emit different colors. The underwater lamp 16 also has a metallic area which is connected to the lamp socket 15, and which in turn has a metallic contact with the tab 3, so that the surface area of the tab 3 is used as a heat radiator, i.e., a cooler, for the underwater lamp 18, the underwater lamp 16 also advantageously having a temperature controller which limits the current, so that the light intensity is decreased and the underwater lamp 16 never overheats.

Of course, the invention is not limited just to the exemplary embodiments illustrated and described.

LIST OF REFERENCE NUMERALS

1 Trim tab

2 Gradation

3 Tab

4 Stern

5 Active cylinder

6 a Gas spring

6 a Gas traction spring

6 b Gas pressure spring

6 c Blockable gas spring

7 Bearing element

8 Breaking edge

9 Side wall

10 Fastening

11 Emergency bolt

12 Opening

13 Reinforcement

14 Lamp support

15 Lamp socket

16 Underwater lamp

17 Check valve

18 Release cable

19 Release head

20 Bracket

21 Edge strip

H Pivot lift

S Flow

WL Waterline

a, b, c Lamp spread angle 

1. Trim tab, wherein, the trim tab has a movable tab on which one or more gradations having breaking edges are mounted, and/or has side walls, and/or the trim tab has a gas spring, and/or an edge strip having a breaking edge which is situated in front of the trim tab is mounted on the stern, and/or the trim tab has at least two underwater lamps which have a spread angle with respect to one another.
 2. Trim tab according to claim 1, wherein, the side walls are mounted on both sides of the tab.
 3. Trim tab according to claim 1, wherein, the tab has an active cylinder and a gas spring, and the gas spring represents a gas traction spring, and the active cylinder must thus exert a force against the gas spring during lowering of the trim tab, or the gas spring represents a gas pressure spring, and assists the active cylinder during lowering of the trim tab, and/or the gas spring represents a blockable gas spring, and has a check valve which is affixed to the release head by means of a release cable so that the gas spring may enable or block the lift.
 4. Trim tab according to claim 1, wherein, the blockable gas spring is unblocked by means of the release head together with the activation of the active cylinder and the blockable gas spring is once again blocked when the active cylinder is stopped.
 5. Trim tab according to claim 1, wherein, the active cylinder is a fluid cylinder or an electric active cylinder having a spindle drive, and the spindle drive is self-locking, or in combination with the blockable gas spring may be nonself-locking.
 6. Trim tab according to claim 1, wherein, the underwater lamp has a metallic housing in whole or in part which is connected to the tab so as to dissipate heat, and/or the underwater lamp has a temperature sensor which reduces the current when a temperature setpoint value is present.
 7. Trim tab according to claim 1, wherein, side walls are mounted on the tab which are at least 50 mm high, or which have at least a height that is practically identical to the outer diameter of the underwater lamps, and water may flow off from the tab. 